Field of the Invention
The present invention relates to a roll feed apparatus for feeding intermittently a sheet-like blank material to a processing station on a step-by-step basis. More particularly, the invention concerns a roll feed apparatus which includes a first roll and a second roll for feeding intermittently a strip-like sheet material to one or more work stations such as metallic molds in a selective manner and which is suited to be incorporated in an automated manufacturing machines or other machine tools.
A known roll feed apparatus of the kind mentioned above comprises a oscillation driving means, a first roll integrally carried by a first roll shaft, a second roll integrally carried by a second roll extending in parallel with the first roll shaft and adapted to cooperate with the first roll in clamping a sheet-like blank material therebetween such as to feed the sheet-like blank material, a connecting device for operatively connecting the oscillation driving device to the first and second rolls such that, when the first roll rocks in one direction by a predetermined amount, the second roll rocks in the opposite direction by an amount substantially equal to the oscillation of the first roll, and a roll release device adapted for moving the first and second rolls away from each other thus releasing the clamping force of the first and second rolls on the sheet-like blank material.
This type of roll feed apparatus is shown, for example, in the specification of the U.S. Pat. No. 4,475,678. This roll feed apparatus provides a considerably high precision of feed of the sheet-like blank material during the high-speed operation. However, since the driving connecting device for operatively connecting both rolls includes a pair of gears, it is quite difficult to completely eliminate any impairment of feeding precision attributable to the presence of back-lash in the meshing gears. In addition, an expensive and heavy coupling has to be used in order to allow both rolls to be moved towards and away from each other for clamping and releasing the sheet-like blank material, while maintaining the driving connection between both rolls through the pair of gears.
Our co-pending U.S. patent application Ser. No. 519,174 filed on Aug. 1, 1983 discloses a roll feed apparatus which eliminates the drawbacks of the prior art shown in the above-mentioned United States Patent and ensures a higher precision of feed.
More specifically, in this roll feed apparatus, the driving connecting device includes a first oscillation arm mounted on the first roll shaft and driven by the oscillation driving device such as to oscillate together with the first roll shaft and the first roll, a second oscillation arm mounted on the second roll shaft and disposed substantially on the same plane as the first oscillation arm, a guide member disposed near the point of intersection between the above-mentioned plane and the path of feed of the sheet-like blank material and provided with a guide groove extending in the direction of feed of the sheet-like blank material, a slider slidable in the guide groove, and a first link and a second link connecting the slider to the first and second oscillation arms, the first and second link being arranged substantially in symmetry with each other with respect to the plane of path of feed of the sheet material, at such an inclination to the plane as to form a shape like V having an apex located at the position of the slider.
This known roll feed apparatus, however, still suffers from problems or deficiencies in that it requires too many movable parts or link members constituting the driving connection device and in that the synchronism of operation of two rolls may be lost due to the fact that the second roll is not directly driven by the oscillation driving device but is driven by the power derived from the first roll and transmitted thorugh the driving connection means. These deficiencies constitute a bottleneck in the attainment of a further improvement in the feeding precision.